(1) Field of the Invention
The present invention relates to a variable displacement oil pump applicable to a hydraulic pressure source from which oil is supplied to, for example, respective slide sections of an internal combustion engine for use in an automotive vehicle.
(2) Description of Related Art
A Japanese Patent Application first Publication No. 2014-105623 exemplifies a previously proposed variable displacement oil pump applicable to the internal combustion engine of the automotive vehicle.
That is to say, in this variable displacement oil pump, a main gallery pressure of the engine, namely, a hydraulic pressure of drained oil after a passage of an oil filter is fed back to a pair of first and second control oil chambers partitioned between a pump housing and a cam ring so as to be mutually opposed so that an eccentricity of the cam ring is variably controlled according to the main gallery pressure. Thus, an energy loss based on a difference pressure between the drain pressure and the main gallery pressure during a drive of the pump is reduced.